arXiv subjects

Chun-Sheng An

Publications and source records attributed to Chun-Sheng An.

At least 19 recordsLinked to original sources

arXiv2026

Heavy dibaryons $\Xi^{()}_{cc}\Xi^{()}_{cc}$ and $\Xi^{()}_{bb}\Xi^{()}_{bb}$

We systematically investigate the dibaryons $\Xi^{(*)}_{cc}\Xi^{(*)}_{cc}$ (di-$\Xi_{cc}$) and $\Xi^{(*)}_{bb}\Xi^{(*)}_{bb}$ (di-$\Xi_{bb}$), with various isospin-spin configurations $I(J^P)$ in a nonrelativistic quark model. For the di-$\Xi_{cc}$ system, only the single channels $\Xi_{cc}\Xi^*_{cc}$ and $\Xi^*_{cc}\Xi^*_{cc}$ with $0(1^+)$ are capable of forming deuteronlike bound states, with the $\sigma$ meson exchange playing a decisive role. Those states have binding energies of approximately $-1.5$ MeV and $-3.3$ MeV and sizes of 2.37 fm and 1.87 fm, respectively. The coupled channel effect in the di-$\Xi_{cc}$ system with $0(1^+)$ enhances the attraction. As a result, this di-$\Xi_{cc}$ system can establish a deuteronlike configuration, with the binding energy of $-7.5$ MeV relative to the threshold $\Xi_{cc}\Xi_{cc}$ and the size of approximately 1.40 fm. For the di-$\Xi_{bb}$ system, the single channels with $0(1^+)$, $0(2^+)$, and $0(3^+)$ can give rise to deuteronlike bound states with binding energies ranging from $-6.1$ MeV to $-14.3$ MeV. Additionally, the di-$\Xi_{bb}$ system with $1(0^+)$ and $1(2^+)$ can also establish deuteronlike bound states with binding energies of around $-0.5$ MeV. When considering the coupled channel effect in the di-$\Xi_{bb}$ system with $0(1^+)$, a compact hexaquark state is formed, exhibiting a binding energy of $-21.2$ MeV relative to the threshold $\Xi_{bb}\Xi_{bb}$ and a size of 0.53 fm. In this state, the $\pi$ meson exchange provides a very powerful attractive force. The meson exchange interactions in the quark model is dispensable in the di-$\Xi_{bb}$ bound states, except for $\Xi_{bb}^*\Xi_{bb}^*$ with $1(0^+)$.

hep-ph↗

arXiv2026

Low-energy $N\phi$ scattering from a pole-enhanced triangle diagram

We investigate low-energy $N\phi$ scattering driven by a pole-enhanced triangle-like diagram, in which the two-Kaon-exchange contribution is promoted by the near-threshold $\Lambda(1405)$ pole in the $N\bar K$ subsystem. Using an unphysical Kaon mass motivated by lattice simulations, we evaluate the $N\phi$ scattering length and find that this mechanism generates an attractive interaction with a magnitude of $-1.1$ to $-0.5\, \rm{fm}$. Spin-dependent effects are not treated explicitly and are expected to provide subleading corrections in the near-threshold region. We further analyze the low-energy behavior of the triangle-like diagram amplitude and show that the scattering length depends on the parameter $\delta$, defined as the mass difference between the $K\bar K$ threshold and the $\phi$ meson, and the pole position of $\Lambda(1405)$, where the $\Lambda(1405)$ plays a crucial role to understand $N\phi$ interaction. Furthermore, by employing physical hadron masses, our calculated scattering length is found to be consistent with current experimental data, providing a unified description across both unphysical and physical mass regimes. This type of interaction differs from that associated with van der Waals-type forces or the long-range tail of two-pion exchange, highlighting the role of three-body dynamics encoded in the pole-enhanced triangle-like diagram in shaping the near-threshold $N\phi$ interaction.

hep-ph↗

arXiv2025

Reevaluating the $a_1(1420)$ enhancement and its molecular partners in the low-lying axial-vector meson spectrum

We assess possible axial-vector states with $G$-parity $\left(G=\pm 1\right)$ dynamically generated by pseudoscalar-vector interactions in coupled channels, driven by the Weinberg-Tomozawa term at leading order in chiral perturbation theory. The $S$-wave amplitudes are unitarized via the Bethe-Salpeter equation, and poles of the unitarized amplitudes are searched for in the complex energy plane. In the isovector sector with $I^G(J^{PC})=1^{\pm}(1^{+\mp})$, we identify two poles around 1400 MeV in the second Riemann sheet below the $K^*\bar{K}$ mass threshold. The $G=+1$ and $G=-1$ poles can be one of the origins of the peaks in the $f_0(980)\pi$ and $\phi\pi^0$ mass spectra reported by the COMPASS and BESIII collaborations, respectively, in the $\pi N \to \pi\pi\pi N$ and $J/\psi \to \eta \phi\pi$ processes, in addition to triangle singularity effects discussed in the literature. Additionally, the poles in the isoscalar sector may explain the nontrivial behavior of the $K^*\bar{K}$ spectra line shapes measured by several experiments in different reactions. Specifically, for the $0^+(1^{++})$ case, we find a sizeable $K^*\bar{K}$ component for the $f_1(1420)$. In the $0^-(1^{+-})$ scenario, the pole strongly coupled to $\rho\pi$ can be associated with the $h_1(1170)$ resonance. Lastly, in this same sector, we identify a higher pole that dominates the $K^*\bar{K}$ invariant mass in the $\chi_{cJ} \to \phi K^*\bar{K}$ decay, where the $h_1(1415)$ is observed in the BESIII data.

hep-ph↗

arXiv2025

The low-lying light tetraquark states with quantum numbers $J^{P}=0^{+ }$, $1^{+}$ and $2^{+}$

The low-lying light tetraquark states are investigated in the non-relativistic quark model (NRQM) including the pseudoscalar meson exchange, where two different confinement potential schemes, the Cornell potential and the linear potential, are employed, along with the instanton-induced interaction serving as the residual spin-dependent interaction. The numerical results show agreement with masses of $f_{0}(500)$, $f_{0}(1370)$, $f_{0}(1500)$, $f_{0}(2020)$, $f_{0}(2200)$, $h_{1}(1170)$, $h_{1}(1595)$, $h_{1}(1900)$, $h_{1}(1965)$, $h_{1}(2215)$, $f_{2}(1430)$, $f_{2}(1640)$, $f_{2}(1810)$, $f_{2}(2010)$, $f_{2}(2150)$, $a_{0}(980)$, $a_{0}(1450)$, $a_{0}(1950)$, $a_{1}(1260)$, $a_{1}(1640)$, $a_{2}(1700)$, $K^{*}_{0}(1430)$, $K^{*}_{0}(1950)$, $K_{1}(1270)$, $K_{1}(1440)$, $K_{1}(1650)$, and $K^{*}_{2}(1980)$. The results shed light on the spectrum of these mesons and offer guidande to search for the tetraquarks in the future.

hep-ph↗

arXiv2025

Hydrogenlike molecules composed of $D_1D_1$, $D_1D^_2$ and $D^_2D^*_2$

We systematically explore the S-wave $D_1D_1$, $D_1D^*_2$ and $D^*_2D^*_2$ states with various isospin-spin-orbit ($ISL$) configurations in the quark model. We propose nine stable dimeson states with the $ISL$ configurations, $ISL=001$, $010$, $012$, $100$, $102$, $110$, $112$, $120$, and $122$, against dissociation into their constituent mesons. Those bound states are hydrogenlike molecular states, where the two subclusters are moderately overlapped and the QCD covalent bond is formed due to the delocalization of light quarks. The QCD covalent bond serves as the primary binding mechanism in the bound states with $I=1$. However, the exchange of $\pi$ and $\sigma$-meson plays a pivotal role in the bound states with $I=0$. The coupled-channel effect is essential in the formation of the bound states with $ISL=001$, $010$, $012$, $100$, and $102$.

hep-ph↗

arXiv2024

Tri-meson state $\boldsymbol{\bar{B}\bar{B}^\bar{B}^}$

We systematically explore the trimeson states $\bar{B}\bar{B}^*\bar{B}^*$ with various isospin-spin configurations in the quark model by solving exactly the six-body Schr\"{o}dinger equations with the Gaussian expansion method. The configuration $\left[[\bar{B} \bar{B}^*]^1_0\bar{B}^*\right]^0_{\frac{1}{2}}$ is not only approximately 10.2 MeV lower than the threshold of its constituent particles but also about 0.2 MeV below that of the compact tetraquark state $[\bar{B}\bar{B}^*]^1_0$ and $\bar{B}^*$. This configuration manifests a loose two-body bound state composed of $[\bar{B}\bar{B}^*]^1_0$ and $\bar{B}^* $, with a size of around 4.75 fm. In contrast, the configurations $\left[[\bar{B}\bar{B}^*]^1_1\bar{B}^*\right]^0_{\frac{1}{2}}$, $\left[\bar{B}[\bar{B}^*\bar{B}^*]^0_1\right]^0_{\frac{1}{2}}$, and $\left[[\bar{B}\bar{B}^*]^1_1\bar{B}^*\right]^1_{\frac{1}{2}}$ exhibit binding energies of less than 1 MeV relative to their constituent particles, establishing a loose three-meson bound state. After coupling three configurations with $\frac{1}{2}0^-$, the trimeson state with $\frac{1}{2}0^-$ remains a loosely two-body bound state with a binding energy around 1.5 MeV and a huge size of 2.20 fm, in which the configuration $\left[[\bar{B}\bar{B}^*]^1_0\bar{B}^*\right]^0_{\frac{1}{2}}$ is dominant, contributing $80\%$ to the overall probability. Among the four bound configurations, the $\sigma$-meson exchange plays a decisive role. The meson pair $[\bar{B}\bar{B}^*]^1_0$, resembling the short-range strong correlated $p$-$n$ pair in nuclear physics, prevails over other types of meson pairs. The meson pair $[\bar{B}\bar{B}^*]^1_0$ not only contributes to the binding mechanisms but also influences the spatial structures of those stable trimeson configurations.

hep-ph↗

arXiv2024

Theoretical study on low-lying hidden-bottom and double-bottom tetraquark states

We perform a theoretical study on the spectrum of the low-lying hidden-bottom ($q\bar{q}b\bar{b}$ with $q=$ $u$, $d$ and $s$) and double-bottom ($q\bar{q}bb$) tetraquark states within a nonrelativistic quark model, in which the instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. All the model parameters are fixed by fitting the spectrum of the ground hadron states. The numerical results indicate that masses of several $X_{q\bar{q}}$, $Z_{b}$, and $Z_{bs}$ tetraquark states are below and near thresholds of corresponding meson-meson channels, thus these states may form components of exotic meson states with reasonable probabilities. Especially, in present model, masses of several obtained states with quantum number $I^G(J^P)=1^+(1^{+})$ are close to $Z_b^\pm(10610)$, so one may expect these states to be non-negligible components of the experimentally observed $Z_{b}$ states. Concerning to the double-bottom tetraquark states, the present results are in general consistent with other previous works. Two possible stable $T_{bb}$ states with quark content $bb\bar{n}\bar{n}$ ($n=u$ or $d$ quark) lying at energies $10558$ MeV and $10650$ MeV are found, and one possible stable $bb\bar{n}\bar{s}$ state is found, whose energy is $\sim10687$ MeV.

hep-ph↗

arXiv2024

$P$-wave states $T^-_{bb}$ from diquarks

We investigate the $P$-wave states $T^-_{bb}$ in the isospin singlet and three excited modes [excitation occurring in the diquark $[bb]^{s_1}_{c_1}$ ($ρ$-mode), antidiquark $[\bar{u}\bar{d}]^{s_2}_{c_2}$ ($r$-mode) or between them ($λ$-mode)] from diquarks in a quark model. We analyze the dynamical behaviors of the diquark $[bb]^{s_1}_{c_1}$, antidiquark $[\bar{u}\bar{d}]^{s_2}_{c_2}$ and their correlations in the states $T^-_{bb}$ by decomposing the interactions from various sources in the model. The absolute dominant color-spin configuration, more than $99\%$, in the $ρ$-mode with $1^1P_1$ is $[bb]^0_{\bar{\mathbf{3}}}[\bar{u}\bar{d}]^0_{\mathbf{3}}$. Its energy is lower by about $18$ MeV than the threshold $\bar{B}\bar{B}$ so that it can establish a compact bound state. The chromomagnetic and meson-exchange interactions in the antidiquark $[\bar{u}\bar{d}]^0_{\mathbf{3}}$ are responsible for its binding mechanism. Two other excited modes are higher than their respective threshold. The color configuration $\mathbf{6}\otimes\bar{\mathbf{6}}$ need to be handled discreetly in the tetraquark states.

hep-ph↗

arXiv2023

Production of $X_b$ via $Υ(5S, 6S)$ radiative decays

We investigate the production of $X_b$ in the process $Υ(5S,6S)\to γX_b$, where $X_b$ is assumed to be a $B {\bar B}^*$ molecular state. Two kinds of meson loops of $B^{(*)}{\bar B}^{(*)}$ and $B_1^{\prime}{\bar B}^{(*)}$ were considered. To explore the rescattering mechanism, we calculated the relevant branching ratios using the effective Lagrangian based on the heavy quark symmetry. The branching ratios for the $Υ(5S\,,6S) \to γX_b$ were found to be at the orders of $10^{-7} \sim 10^{-6}$. Such sizeable branching ratios might be accessible at BelleII, which would provide important clues to the inner structures of the exotic state $X_b$.

hep-ph↗

arXiv2023

The quark orbital angular momentum of ground state octet baryons

Here we study the quark orbital angular momentum of the ground octet baryons employing an extended chiral constituent quark model, within which the baryon wave functions are taken to be superposition of the traditional $qqq$ and the $qqqq\bar{q}$ higher Fock components. Coupling between the two configurations is estimated using the $^3P_{0}$ quark-antiquark creation mechanism, and the corresponding coupling strength is determined by fitting the sea flavor asymmetry of the nucleon. The obtained numerical results show that the quark angular momentum of the nucleon, $Σ$, $Λ$ and $Ξ$ hyperons are in the range $0.10$-$0.30$. In addition, the quark angular momentum of all the hyperons are a little bit smaller than that of the nucleon. And the octet baryons spin fractions taken by the intrinsic quark orbital angular momentum could be up to $60\%$ in present model.

hep-ph↗

arXiv2022

Spectrum of the S-wave fully-heavy tetraquark states

In present work, spectrum of the $S$-wave fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q=c,b$), i.e., $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$, $bc\bar{c}\bar{c}$/ $cc\bar{b}\bar{c}$, $bb\bar{c}\bar{b}$/$cb\bar{b}\bar{b}$, and $bc\bar{b}\bar{c}$ are systematically investigated within an nonrelativistic constituent quark model, in which the Instanton-induced and one-gluon-exchange interactions are taken into account as the residual spin-dependent hyperfine interaction. Our results show that the states with $cc\bar{c}\bar{c}$ and $bb\bar{b}\bar{b}$ components could be located around $ 6500$ MeV and $ 19200$ MeV, respectively. Based on our calculations, the new $X(6900)$ state observed by LHCb may be not a ground $cc\bar{c}\bar{c}$ tetraquark state, while it could be an orbitally or radially excited state of $cc\bar{c}\bar{c}$ system. On the other hand, the recently reported $X(6600)$ state by CMS and ATLAS can be explained as a ground $cc\bar{c}\bar{c}$ tetraquark state with spin-parity $J^{PC} =0^{++}$.

hep-ph↗

arXiv2022

Color flux-tube nature of the states $T_{cs}(2900)$ and $T^a_{c\bar{s}}(2900)$

Inspired by the states $T_{cs0}(2900)^0$, $T_{cs1}(2900)^0$, $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ reported by the LHCb Collaboration, we carry out a systematical investigation on the properties of the ground and $P$-wave states $[cs][\bar{u}\bar{d}]$ and $[cu][\bar{s}\bar{d}]$ with various spin, isospin or $U$-spin, and color combinations in a multiquark color flux-tube model. Matching our results with the spin-parity and mass of the states $T_{cs0}(2900)^0$ and $T_{cs1}(2900)^0$, we can describe them as the compact states $[cs][\bar{u}\bar{d}]$ with $I(J^{P})=1(0^+)$ and $0(1^-)$ in the model, respectively. The ground state $T_{cs0}(2900)^0$ is mainly made of strongly overlapped an axial-vector $[cs]_{\bar{\mathbf{3}}_c}$ and an axial-vector $[\bar{u}\bar{d}]_{\mathbf{3}_c}$. The $P$-wave state $T_{cs1}(2900)^0$ is dominantly consisted of a gradually separated scalar or axial vector $[cs]_{\bar{\mathbf{3}}_c}$ and a scalar $[\bar{u}\bar{d}]_{\mathbf{3}_c}$ in the shape of a dumbbell. Supposing the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ belong to the same isospin triplet, the mass of the state $\left [[cu]_{\bar{\mathbf{3}}_c}[\bar{s}\bar{d}]_ {\mathbf{3}_c}\right ]_{\mathbf{1}_c}$ with symmetrical $U$-spin and $J^P=0^+$ is highly consistent with that of the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ in the model. After coupling two color configurations, the state $[cu][\bar{s}\bar{d}]$ is slightly lighter than the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$. In addition, we also discuss the properties of other states in the model.

hep-ph↗

arXiv2022

Radiative decays of the neutral $Z_c(3900)$ and $Z_c(4020)$

We study the radiative decays $Z_c(3900)/Z_c(4020) \to γχ_{cJ}(γχ_{cJ}^\prime)$ ($J=0, 1, 2$), with the assumption that the $Z_c(3900)$ and $Z_c(4020)$ couple strongly to $D\bar D^* +c.c$ and $D^*{\bar D}^*$ channel, respectively. By considering the contributions of intermediate charmed mesons triangle loops within an effective Lagrangian approach, it is shown that the calculated partial widths of $Z_c(3900) \to γχ_{cJ}$ are about a few hundreds keVs, while the obtained partial widths $Z_c(4020) \to γχ_{cJ}$ are about tens of keVs. The predicted partial widths of $Z_c(3900)\toγχ_{c0,1}^\prime$ are less than 1 keV, which mainly due to the very small phase space. For $Z_c(4020)\toγχ_{c0,2}^\prime$, the calculated partial widths are usually smaller than 1 keV. For the $Z_c(4020)\toγχ_{c1}^\prime$ process, the obtained partial widths can reach up to the order of 10 keV. Furthermore, the dependence of these ratios between different decay modes on the masses of $Z_c(3900)$ or $Z_c(4020)$ are also investigated, which may be a good quantity for the experiments. It is hoped that these calculations here could be tested by future experiments.

hep-ph↗

arXiv2022

Investigations on the charmless decays of $X(3872)$ in intermediate meson loops model

The charmless decay processes of $X(3872)$ provide us a good platform to study the nature and the decay mechanism of $X(3872)$. Based on a molecular nature of $X(3872)$ as a $\bar{D}D^*$ bound state, we have investigated the charmless decays $X(3872) \to VV$ and $VP$ via intermediate $D^*{\bar D} +c.c.$ meson loops, where $V$ and $P$ stand for light vector and pseudoscalar mesons, respectively. We discuss three cases, i.e., pure neutral components ($θ=0$), isospin singlet ($θ=π/4$) and neutral components dominant ($θ= π/6$), where $θ$ is a phase angle describing the proportion of neutral and charged constituents. The proportion of neutral and charged constituent have an influence on the decay widths of $X(3872) \to VV$ and $VP$. With the coupling constant of $X(3872)$ to the $\bar{D}D^*$ channel obtained under the molecule ansatz of $X(3872)$ resonance, the predicted decay widths of $X(3872)\rightarrow VV$ are about tens of keVs, while the decay width can reach a few hundreds of keVs for $X(3872)\to VP$. The dependence of these ratios between different decay modes of $X(3872)\to VV$ and $X(3872)\to VP$ to the mixing angle $θ$ is also investigated. It is expected that the theoretical calculations here can be tested by future experiments.

hep-ph↗

arXiv2022

The low-lying hidden- and double-charm tetraquark states in a constituent quark model with Instanton-induced Interaction

Spectrum of the low-lying hidden- and double-charm tetraquark states are investigated in a nonrelativistic quark potential model, where the Instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. The model parameters are fixed by fitting the spectrum of the ground hadron states. Our numerical results show that masses of several presently studied tetraquark states are close to those of the experimentally observed candidates of exotic meson, which indicates that the corresponding compact tetraquark components may take considerable probabilities in those observed exotic states.

hep-ph↗

arXiv2022

Investigations on the flavor-dependent axial charges of the octet baryons

We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\bar{q}) (q=u, d, s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}P_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the singlet axial charges of the octet baryons, which should indicate total baryons spin arising from the spin of the quarks, fall in the range $0.45-0.75$ in present model. This is in consistent with the predictions by lattice QCD and chiral perturbation theory. It's also very interesting that the light quarks spin $Δu$ and $Δd$ in the $Λ$ baryon are of small but negative values, which exactly vanish in the traditional three-quark model.

hep-ph↗

arXiv2021

The $Ω_{cc}$ resonances with negative parity in the chiral constituent quark model

Spectrum of the low-lying $Ω_{cc}$ resonances with negative parity, which are assumed to be dominated by $sccq\bar{q}$ pentaquark components, is investigated using the chiral constituent quark model. Energies of the $Ω_{cc}$ resonances are obtained by considering the hyperfine interaction between quarks by exchanging Goldstone boson. Possible $sccq\bar{q}$ configurations with spin-parity $1/2^{-}$, $3/2^{-}$ and $5/2^{-}$ are taken into account. Numerical results show that the lowest $Ω_{cc}$ resonances with negative parity may lie at $4050 \pm 100$ MeV. In addition, the transitions of the $Ω_{cc}$ resonance to a pseudoscalar meson and a ground baryon state are also investigated within the chiral Lagrangian approach. We expect that these $Ω_{cc}$ resonances could be observed in the $\bar{D}Ξ_{c}$ channel by future experiments.

hep-ph↗

arXiv2021

The axial charges of proton within an extended chiral constituent quark model

We have performed a study of the isovector, octet and singlet axial charges of the proton in an extended chiral constituent quark model, where all the possible $uudq\bar{q}$~($q=u,d,s$) five-quark Fock components in the proton wave function are taken into account. The $^3P_0$ quark-antiquark creation mechanism is assumed to account for the transition coupling between three- and five-quark components in proton, and the corresponding transition coupling strength is fixed by fitting the intrinsic sea flavor asymmetry $\bar{d}-\bar{u}$ data for proton. Accordingly, with all the parameters fixed by empirical values, the probabilities of the intrinsic five-quark Fock components in proton wave function should be $\sim30 - 50\%$, which lead to the numerical results for quark spin $Δu$, $Δd$ and $Δs$, as well the axial charges of proton consistent with the experimental data and predictions by other theoretical approaches.

hep-ph↗